The role of diapause in the remarkable adaptation of the tarnished plant bug to its environment in the mid-South
USDA-ARS, Stoneville, MS, USA
Correspondence: gordon.snodgrass@ars.usda.gov
Tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), overwinter as diapausing adults throughout North America. Because of the importance of diapause in the development of control methods for plant bugs, diapause in the tarnished plant bug was studied from 1999–2007 in field and laboratory tests at Stoneville, MS. Stoneville is at a latitude of 33.43 N and is in Washington County near the western edge of MS in the Mississippi River Delta. Tarnished plant bugs begin entering diapause at Stoneville in late August and by 12 September about 50% of the developing nymphs will produce diapausing adults. Most nymphs developing in the field at the shorter day lengths found in October and November become diapausing adults. However, reproduction in the fall continues in the field on weed hosts until the hosts are killed by a freeze or senescence occurs. Reproduction can also occur during the winter with new generation adults produced in March in mild winters. Tarnished plant bugs are able to break diapause and utilize favorable weather conditions to reproduce in the fall and winter in the mid-South because of two factors. One factor is the presence of abundant wild hosts that bloom in October and November along with winter hosts (mainly henbit, Lamium amplexicaule L.) that bloom in late November through March. The other factor is the ability of diapausing adult tarnished plant bugs to break diapause under a diapausing-inducing day length in response to temperature and food stimuli. Both of these stimuli are important, and food must contain nutrients as are found in blooms or flower buds. The laboratory and field tests that determined the importance of food and temperature in the emergence of plant bugs from diapause and how this makes plant bugs so well adapted to their environment in the mid-South are discussed.